Different perspectives, was: Rain-X on module glass? [RE-wrenches]

Ezra Auerbach, DragonSun Consulting ezra at lasqueti.net
Fri Jan 9 13:23:50 PST 2004


I have to chime in here in full agreement with Christopher on the
benefits of wiring the PV array nominal 72 Vdc for 48 Vdc or less
battery voltage.  My 24 Vdc system has one of the two sub arrays wired
that way and when in partial shade (it is winter here in the lower
north) the Max Power tracks down at 65 Vdc which is still more than
enough to be converted into useable 24 Vdc amps by the controller.  

Regards to all,
Ezra Auerbach


-----Original Message-----
From: Christopher Freitas --- OutBack Power
[mailto:cfreitas at outbackpower.com] 
Sent: Friday, January 09, 2004 11:52 AM
To: RE-wrenches at topica.com
Subject: RE: Different perspectives, was: Rain-X on module glass?
[RE-wrenches]


Good point Windy - This is one of the benefits of wiring up the PV array

for 72 vdc nominal (three 24vdc modules in series) with a 48 vdc battery

system for instance (or lower).

Another way to look at it - as long as the peak power point of the PV 
array stays above the battery voltage - the losses are minimal 
(proportional to the temperature).  If the peak power point drops below 
the battery voltage - then you start losing lots more power.  

When you start with a peak power point of 90 vdc or so - it has to be 
really hot for it to get down to the 50 volt level ;-)

Christopher Freitas
OutBack Power Systems, Inc.
cfreitas @ outbackpower.com  
www.outbackpower.com
Arlington WA USA
Tel 360 435 6030  

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